Thermographic copying machine



Sept. 22, 1964 J. w. ULSETH ETAL 3,150,262

.THERMOGRAPHIC COPYING MACHINE Filed April 5, 1960 3 Sheets-Sheet 1INVENTORS'. ROBERT A. HALBERG JOHN W. ULSETH BY JOHN A. GRAY/ELLEATTORNEYS Sept. 22, 1964 J, w. ULSETH ETAL THERMOGRAPHIC COPYING MACHINE5 Sheets-Sheet 2 Filed April 5, 1960 INVENTORS. ROBERT A. HALBERG JOHNW- ULSETH JOHN A. GRAVELLE P 22, 1964 J. w. ULSETH E'IAL 3,150,262

THERMOGRAPHIC COPYING MACHINE Filed April 5, 1960 3 Sheets-Sheet 5 m \na INVENTORS.

7 ROBERT A. HALBERG N w. ULSETH N A. GRAVELLE w/zmww ATT ORNEYS U d s PWe Patented Sept. 22, 1964 FIGURE 1. Disposed between the pressure roll18 and 3,150,262 the rolls 21 and 22 is a thin walled radiant energytrans THERMOGRAPHIC COPYING MACHINE John W. Ulseth, St. Paul, Robert A.Halberg, West St- Paul, and John A. Gravelle, Roseville, Minn, assignorsto Minnesota Mining and Manufacturing Company, St. Paul, Minn, acorporation of Delaware Filed Apr. 5, 1960, Scr. No. 20,039 12 Claims.(Cl. 250-65) This invention relates to improvements in thermographiccopying machines and has particular reference to a low cost machinecapable of rapidly and efficiently producing any desired number ofreproductions of graphic originals on heat sensitive copy paper. Theimproved machine is light in weight and readily portable, havingphysical dimensions approximating those. of a portable typewriter. Thelow contour of the improved machine makes it particularly suited todesk-top use.

compactness is lent to the improved machine by the embodiment therein ofa transparent tubular copy roll within which a lamp and reflectorassembly is mounted, there being means forpressing a composite ofgraphic original and copy sheet into intimate contact with the outersurface of the copy roll as the composite passes the area in which theirradiation of the lamp is concentrated by the reflector assembly. Theimproved machine has variable speed means and is provided with a singlecontrol knob which affords selective control of energization of both thelamp and the drive motor as well as selective control of the position ofthe lamp and reflector assembly and the speed at which the copy roll isdriven. The efficiency of the machine is enhanced by the use of a novelreflector construction affording improved reflectance and stabilitycharacteristics, as well as by the use of a novel copy roll constructiontending to insure Wrinkle free composite orientation during travelthrough the machine and particularly during irradiation.

The invention can best be understood by reference to the accompanyingdrawings illustrating one complete embodiment of the presently preferredform of the invention in which:

FIGURE 1 is a plan view showing the improved thermocopying machine withthe cover removed, parts being broken away and shown in section;

FIGURE 2 is a vertical sectional view of the improved machine takengenerally along the line II-II of FIG- URE l;

FIGURE 3 is a perspective view showing the coordination of certain ofthe parts of the improved machine which are under the control of thesingle control knob;

FIGURE 4 is an enlarged vertical sectional View taken through the lampand reflector assembly of the improved machine; and

FIGURE 5 is a greatly enlarged fragmentary plan view of the copy roll toshow the variation in the diameter of said roll.

Referring more particularly to FIGURES 1 and 2, the form of the improvedcopying machine selected for illustration therein comprises arectangular base member and a complemental rectangular removable cover11 (FIGURE 2). Mounted on the base 10 is a frame 12 having opposite endwalls 13 and 14, a rear wall 15 and apertured front and top walls 16 and17 respectively.

Mounted in suitable bearings carried by the frame end walls 13 and 14 isa pressure roller 18 comprising a metal rod or shaft 19 having bondedthereto a thick cylindrical sleeve'Zt) of very soft resilient material,for example very soft rubber. Also mounted in suitable bearings carriedby the frame end walls 13 and 14 are a pair of spaced rubber coveredrolls 21 and 22, the roll 21 having an integral drive shaft 23 whichextends beyond the frame end wall ,14.and carries adrive pulley 24 asshown in missive copy roll 25 for example of heat resistant glass. Itwill be observed in FIGURE 2 that the spacial relationship between therolls 1%, 21 and 22 is such that the copy roll 25 deforms the pressureroll 18 to form a nip area of substantial width extending the fulllength of the roll 18. In the presently preferred form of the invention,the pressure roll 18 is 2 inches in diameter, the copy roll 25 is 1.780inches in diameter and 0.055 inches in wall thickness. The nip area isinch in width and the pressure contact between the rolls 1S and 25across the nip varies from 0 to- 9 pounds per square inch, the pressurecurve being sinusoidal with the pressure peak at the midpoint of thenip.

The rolls 18, 21 and 22 constitute the bearings for the copy roll 25,the latter being prevented from substantial axial movement by suitablethrust bearing members (not shown) engageable therewith and carried byframe end walls 13 and 14. The copy roll 25 is driven in a clockwisedirection as viewed in FIGURE 2 by the roller 21 which, in turn, isdriven by an endless belt 26 which connects the pulley 24 to the outputdrive pulley 27 of variable speed drive means comprising a variablespeed transmission 28 and a drive motor 29. The variable speedtransmission 28 has a frame 28a comprising spaced parallel wall members3th, 31 and 32. held in assembled relation by rods 33 and 34 fixedthereto. The motor drive shaft 41 extends through the frame wall 30 andcarries a gear type pulley 35. A generally u shaped carrier member 36 isformed with a pair of spaced parallel side plate members 37 and 38 andwith a transverse connecting plate member 39 having an intermediateplate member 40 stamped therefrom and extending parallel with sideplates 37 and 38. The carrier member 36 is bearinged on the Wall members3% and 31 for pivotal movement about the axis of the motor drive shaft41. The intermediate plate member 49 is provided with suitable bearingmeans for supporting a short shaft 42 which carries a gear type pulley43 on one side of the plate 40 and a shallow slope driving cone 44 onthe other side. An internally toothed endless belt 45 connects the motordrive pulley 35 to the pulley 43 to afford a positive driving connectionbetween the motor 29 and the cone 44. Fixed to the side plate 38 of thecarrier 36 is a gear quadrant 46 which is in toothed engagement with alongitudinally slidable rack 47 for a purpose to be later described.

A shaft 48 is axially slidably mounted in suitable bearings in the framemembers 31 and 32 and has fixed to one end thereof an enlarged disc 49carryinga peripheral facing ring 50 of frictional material. The facingringSt) of the disc 49 is biased into frictional engagement with thecone 44 by a leaf spring 51 fixed atone end tothe frame member 32 andhaving its free end engaging the end of the shaft 48 opposite the disc49. The output pulley 27 is carried by a shaft 52 mounted in suitablebearings carried by frame members 31' and 32, said shaft also carrying agear 53 which meshes with an elongated gear 54 fixed on the shaft 48,all as shown in FIGURE 1.

It will be observed in FIGURE 2 that the axis of the motor shaft 41 isspaced below and parallel with the axis of the shaft 48. When the partsare in the position the dot and dash line position thereof shown inFIGURE 2, the annular frictional facing 50 contacts the cone 3 V 44 nearthe apex thereof so that the copy roll 25 is driven at minimum speed fora given speed of rotation of the motor drive shaft 411. Between thesetwo limits,

the speed of the copy roll 25 can be varied infinitely in accordancewith the position of the rack 47 intermediate the solid line and dot anddash line extreme positions thereof shown in FIGURE 2. V

The base member 16 is provided with slidable mounting means for anelongated channel shaped actuating or slide member 55 having fixedthereto a manually engageable control knob 56. A Bowden wire '7 has oneend fixed to the rack 47 and extends through a sheath 58 fixed to abracket 58a (FIGURES 1 and 2) on base member 10, said Bowden wire havingits opposite end fixed to the slide member 55 as at the screw 59. Itwill be observed that the position of the slide 55 and control knob 56shown in solid lines in FIGURE 1 and shown in dot and dash lines inFIGURE 3 afiords maximum speed of the copy roll because'this positioncorresponds to the solid line positionsof the parts in FIGURE 2.,Movement of the knob 56 and thereby of the slide 55 to the left of theposition shown in solid lines in FIGURE 3 moves the rack 47 forwardly tothe position shown in dot and dash lines in FIGURE 2 and pivotsthequadrant 46 to the position shown in FIGURE 3, correspondinglypivoting the carrier 36 as aforedescribed.

A normally closed electrical switch 69 is suitably mounted on the base10 and has a depressable button 61 positioned to be depressed by a cammember 62 formed on the adjacent end of the slide member 55 and formingan extension of the rear flange thereof. The switch 66 is connected incircuit with the motor 2% and with a source of alternating current bymeans (not shown) which may include a step-up transformer 63. When theslide is moved to the left to the extreme position shown in solid linesin FIGURE 3, the button 61 of switch 66 is depressed to open the circuitto the motor 29 and prevent energization thereof. It is apparent,therefore, that movement of the knob 56 to the right from the dot anddash line off position of FIGURE 1 effects closure of the contacts ofthe switch 60 and operation of the motor 29 with concomitant rotation ofthe copy roll 25 at a speed depending upon the distance the knob 56 hasbeen moved toward its solid line position shown in FIGURE 1.

The base member It) and frame 12 are provided with means at the front ofthe machine defining an inlet throat 64 through which a composite of agraphic original and copy sheet (not shown) can be introduced and bywhich such composite is guided toward the underside of the nip of thepressure roll 18 and copy roll 25. Above the aforementioned nip, thecover 11 is provided with an outlet throat 65 through which a compositeis guided from the nip of rolls 18 and 25.

Means is provided for subjecting a composite of graphic original andcopy sheetto brief intense irradiation while passing through the nip ofthe rolls 18 and 25. The preferred irradiating means takes the form of alamp and reflector assembly 66 comprising an elongated tubular lamp 68disposed substantially axially ofra reflector 67, said assembly 66extending within the copy roll 25 as shown in FIGURES l and 2. .Thereflector 67 and lamp 68 of the assembly 66 are fixed relative to eachother and,as shown most clearly in FIGURES l and 3, said assembly issupported at its opposite ends by pivotal arms 69 and 70 which arepivoted, respectively on pins 71 and 72 supported in suitablebearingscarried by:

the side walls 13, and 14 of frame 12 respectively. The assembly 67 isbiased toward its operative position shown j in the solid lines inFIGURE 2 and in dot and, dash lines The mountinga'means for actuatingthereflector and,

lamp "assembly, 66 permits movement thereof from its operative positionclosely adjacent the inner surface of the copy roll 25 at the nip areaof said roll and roll 18 to a retracted inoperative positionsubstantially centrally of the roll 25 and shown in solid lines inFIGURE 3. Means is provided for actuating the lamp and reflectorassembly 66 to its inoperative position against the bias of the spring73 and 74 whenever the knob 56 is moved to its oif position shown insolid lines in FIGURE 3 and dot and dash lines in FIGURE 1. Theactuating means referred to takes the form of a cam member 75 fixed tothe slide 55 and having an angled surface'76 positioned to engage thearm 70 below the pin 72. The parts are so arranged that as the slide 55is moved toward the left as viewed in FIGURES l and 3, the cam surface'76 engages the arm 76 just before the slide reaches its off position.As the slide moves to its off position,

' the cam surface 76 moves the lower end of the arm 70 rearwardly,tilting the upper end of said arm forwardly,

to thereby move the lamp and reflector assembly 66 to its retractedinoperative position shown in solid lines in FIGURE 3. When the knob 56is subsequently moved toward the right from its off position, the camsurface 76 moves out of engagement with the lower end of the arm 70, andthe springs 73 and 74 thereupon return the reflector and lamp assembly66 to the operative position shown in solid lines in FIGURE 2 and dotand dash lines in FIGURE 3.

The use of a thin-walled copy roll 25 and of a movably mounted lamp andreflector assembly 66 as aforedescribed permits the lamp to bepositioned close to the composite and also permits rapid cooling of theparts when in shut-01f position, preventing the development of a hotspot in the roll 25 as a result of absorption of 'heat from the assembly66 such as might occur on shutoff of the machine if the assembly 66 werefixed in its operative position. The occurrence of such a hot spot wouldprevent proper functioning of the machine so long as the hot spotexists, since a composite would be overheated by contact with 'the hotspot as it passes through the machine.

Energization of the lamp 68 is under the control of a normally openswitch 77 (FIGURE 1) provided with a rotatable actuating rod 78extending transversely of the frame 12. A pair of wire bails 7E9 arefixed to the rod 78, as at 86 and 81 respectively, and extend downwardlytherefrom across the inlet throat 64 as shown in FIGURE 2. Insertion ofa composite into the inlet throat 64 swings the balls 79 rearwardly andupwardly to non-obstructing positions, such bail movement simultaneouslyactuating the switch 77 to closed position permitting energization ofthe lamp 68. As the trailing end of the composite enters the nip of therolls 13 and 25, and moves out of contact with the balls 7 said bailsreturn by gravity to the position shown in FIGURE 2, and the switch 77returns to its normally open position effecting extinguishment of thelamp 68. It should bepointed out that the lamp and switch 77 arepreferably in series circuit with the main switch 60 and the source ofelectrical energy, so that the lamp can be energized only if the knob56. is in one of its on positions. It is apparent, therefore, that thesingle control knob 56 is eifcctive to control energization of the lamp68 and motor 29 and is additionally effective to control the speed atwhich the copy roll 25 is driven, as wellas the position of the lamp andreflector assembly 66.

It will be observed that the reflector 67 has a relatively narrowopeningflZ which concentrates the radiant energy from the lamp 68 alonga relatively narrow band of V the nip area of'the rolls 18 and 25. Inthe presently preferred'form 'of the invention'the reflector opening 82'ative position, and the speed with which a composite can be movedthrough the nip of the rolls 18 and 25 can be selectively varied from1.25 to 4.5 inches per second depending upon the position of the controlknob 56.

The reflector 67 is characterized by exceptional reflectivity, i.e.greater than 93 percent reflectance of infrared, excellent heatstability, low cost and light weight. Referring to FIGURE 4, thereflector 67 may be made of a pair of complemental metal shells 67a and67b, preferably of aluminum which may be formed to the desired shape bysuitable machining, extrusion, rolling or other means. The inner surface83 of the reflector 67 is overlaid with a thin layer 84 of lowtemperature porcelain enamel. The layer 84 may be applied by sprayingthe surface 83 with a thin layer of a slip comprising slurry of a lowtemperature frit, an opacifier, suitable suspending or binding agentsand water. The frit preferred for this purpose is a substantially leadfree alkali titania silicate glass of the type commercially availableunder the trade name 3M Brand Aluminum Frit No. 8102. The thickness ofthe layer of slip is preferably held within'close tolerances at 0.002inch in thickness. The reflector 67 is then baked at the slips curingtemperature, i.e. at 9701000 R, which is below the melting temperatureof the aluminum base, and is then allowed to cool. The resulting enamellayer 84 is characterized by an extremely smooth surface with a highgloss. The reflector 67 is then placed in a vapor coating apparatus anda thin film of chromium or nickel containing bonding agent is vaporcoated thereon. Suitable bonding agents are elemental chromium andInconel, an alloy of iron, chromium and nickel. A thin film 85 of goldis then vapor coated onto the surface of the porcelain enamel layer 84bearing the bonding agent, the amount of gold being preferably justsufficient to provide opacity, although slightly less or slightly morethan that required for opacity may be applied. If a bonding agent is notused, the gold layer 85 may be vapor coated directly onto the porcelainenamel layer 84, and a bond therewith can be produced by a second bakingoperation at a temperature just below the 1000 F. softening temperatureof the enamel.

The improved reflector 67 is superior to reflectors heretofore known andin particular is superior to reflectors in which the reflective materialis electroplated directly onto a metallic base, since in the lattertype, surface irregularities in the base are imparted to the reflectivelayer. In the instant reflector, such irregularities are not imparted tothe surface of the enamel layer, which is extremely smooth and glossy.The porcelain enamel layer 84 provides a chemically inert and heatinsulating barrier between the metal of the base 67 and the metal of thereflective layer 85 preventing chemical reaction or alloying of thesemetals which would deleteriously affect the reflective properties of thelayer 85. Since the ceramic layer 84 maintains the barrier even at hightemperatures, the reflector 67 has high temperature stability heretoforeunobtainable. Moreover, the heat insulating qualities of the layer 84prevents excessive heating of the low temperature alloy base 67.

In the operation of the improved machine, it is important that thecomposite lay flat against the copy roll 25 as it passes through the nipof the rolls 18 and 25.

A number of factors, however, tend to create wrinkling of the compositeas it passes through the nip, such factors including embossing, letterfolds, high moisture content and mill formed moisture wrinkles in theoriginal or copy paper. Surprisingly, it has been found that by formingthe copy roll 25 in a novel manner, such factors can be prevented fromcausing wrinkling of the composite. To this end the copy roll preferablyhas an average profile in axial section which is radially inwardly bowedfrom its ends toward the central portion thereof. The bow referred to istermed negative bow and it defined in terms of inches of external radiusof the central portion of the roll less than the radius of a perfectcylinder having a radius corresponding to that of the ends of the rollinwardly of any terminal bead thereon. The average negative bow ispreferably at least 0.00015 inch per inch of length of the roll 25, and0.001 inch per inch of diameter of said roll. In the embodiment of theinvention illustrated, i.e. one in which the roll 25 is 10 inches inlength, and 1.780 inches in diameter at the ends, a negative bow of0.004 inch has been found effective to prevent wrinkling of a compositepassing through the machine.

What is claimed as the invention is:

1. In a thermographic copying machine having means including a rolldefining a copy station, means for irradiating a composite of a graphicoriginal and a copy sheet while in contact with said roll, said meanscomprising a lamp assembly, means mounting said lamp assembly formovement between an operative position closely adjacent a surface ofsaid roll and a retracted position spaced away from said roll surface,drive means for said roll, and actuating means operatively associatedwith said mounting means and said drive means for actuating said lampassembly to operative position when operation of said drive means isinitiated and to retracted position when operation of said drive meansis terminated.

2. In a thermographic copying machine having means including a rolldefining a copy station, means for irradiating a composite of a graphicoriginal and a copy sheet while in contact with said roll, said meanscomprising a lamp assembly, means mounting said lamp assembly formovement between an operative position closely adjacent a surface ofsaid roll and a retracted position spaced away from said roll surface,drive means for said roll, actuating means operatively associated withsaid mounting means and said drive means for actuating said lampassembly to opervative position when operation of said drive means isinitiated and to retracted position when operation of said drive meansis terminated, and

switch means operatively associated with said lamp assembly permittingenergization thereof when said assembly is in operative position andpreventing ene'rgization thereof when said assembly is in retractedposition.

'3. In a thermographic copying machine having means including a rolldefining a copy station, means for irradiating a composite of a graphic.original and a copy sheet while in contact with said roll, said meanscomprising a lamp assembly, and means mounting said lamp assembly formovement between an operative position closely adjacent a surface ofsaid roll and a retracted position spaced away from said roll surface,drive means for said roll, actuating means operatively associated withsaid mounting means and said drive means for actuating said lampassembly to operative and retracted positions, and manually operatedcontrol means for said drive and mounting means movable between anoffposition in which it effects shutoff of said drive means and retractionof said lamp assembly and an on position in which it effects operationof said drive means and movement of said lamp assembly to operativeposition.

4. A machine according to claim 3 in which there is switch means forsaid lamp assembly also under the control of said manually operatedcontrol means and operable to prevent energization of said lamp assemblywhen said control means is in off position and to permit energization ofsaid lamp when said control means is in on position.

5. In a thermographic copying machine having means including a rolldefining a copy station, means for irradiating a composite of a graphicoriginal and a copy sheet while in contact with said roll, said meanscom prising a lamp assembly, and means mounting said lamp assembly formovement between an operative position closely adjacent a surface ofsaid roll and a retracted position spaced away from said roll surface,variable speed drive means for said roll, manually operated controlmeans movable between an off position and a plurailty of on positionsoperatively associated with said drive means for selectively means ordriving of said roll thereby at a selected speed, and actuating meansfor said mounting means opera= tively associated with said controlmeanstto move said lamp assembly to retracted position on movement ofsaid control means to off position and move said lamp assembly tooperative position on movement of said control means to an on position.t i

6. A thermographic copying machine comprising means including a tubularcylindrical radiant energy transmissive roll defining a copy station,means for irradiating a composite of a graphic original and a copy sheetwhile in contact with the outer surface of said roll, said meanscomprising a lamp assembly extending longitudinally within said roll,means mounting said lamp assembly for movement between an operativeposition closely adjacentv the inner surface of said roll and a radiallyinwardly retracted inoperative position, drive means for rotating saidroll, and single control means which effects movement of said mountingmeans to retract said lamp assembly to said inoperative position andwhich terminates operation of said drive means.

7. A thermographiccopying machine comprising means inner surface of saidroll and a radially inwardly re- 'tracted lnoperative position, andsingle control means which effects movement of said'mounting means toretract said lamp assembly to said inoperative position and whichterminates operation of said drive means.

8. A thermographic copying machine comprising a effecting shutoff ofsaid drive tubular cylindrical radiant energy transmissive roll, meansfor conveying a composite of a graphic original and a copy sheet to andfrom a copy station at which said composite is pressed thereby intointimate contact with a narrow axially extending outer surface portionof said roll,

, operative position closely adjacent the inner surface of said roll andat which the radiation from said lamp is focused on said narrow outersurface'portion'of said roll and a radiallyinwardly retractedinoperative position, and single control means which etects movement ofsaid mounting means to retract said lamp assembly to said moperativeposition and which terminates operation of said conveying means.

9. A thermographic copying machine comprising a tubular cylindricalradiant'energy transmissive glass first roll, drive means for rotatingsaid first roll, a relatively soft resilient second roll parallelwithand in deformed.

pressure contact with said first roll, difining therewith a narrowaxially extending nip area, means for irradiating a composite of agraphic original and a copy sheet compressed against said first roll insaid nip area comprising a lamp assembly extending longitudinally withinsaid first roll, deflector meansfocusing' the radiation from .said lampassembly within a narrow region, means mountmg said lamp assembly formovement between an operative position closely adjacent the innersurface of said roll and at which the radiation from said lamp isfocused on said nip area and a radially inwardly retracted. inoperativeposition,-and single control means which effects movement of saidmounting means to retract said lamp assembly to said inoperativeposition and which terminates operation of said drive means.

10. A thermographic copying machine comprising a tubular cylindricalradiant energy transmissive glass roll, means for conveying a compositeof a graphic original and a copy sheet to and from a copy station at.which said composite is pressed thereby into intimate contact with anarrow axially extending outer surface portion of said roll, means forirradiating said original at said copy station comprising a lampassembly extending longitudinally within said roll, reflector meanspositioned with respect to said lamp for focusing the radiation fromsaid lamp assembly along a narrow band, means mount ing said lampassembly and reflector means for movement relative to said roll betweenan operative'position closely adjacent the inner surface of said rolland at which the narrow band of radiation is focused on the outersurface portion of said roll and an inoperative position spaced radiallyinward from the surface of said roll at which the narrow band ofradiation is not focused along any portion of said roll, and controlmeans for said drive and mounting means movable between an off positionin which it eiiects shutoii of said conveying means and retraction ofsaid lamp assembly and an on position in which it effects operation ofsaid conveying means and movement of said lamp assembly to operativeposition.

11. A thermographic copying machine comprising a copy roll adapted tohavea composite of a graphic original and a copy sheet moved therepastin contact with the periphery thereof; said copy roll being generallycylindrical in shape and having an average profile in axial sectionwhich is radially inwardly bowed from its ends toward the centralportion'thereof, and means for pressing a composite against theperiphery of said copy roll as said composite moves therepast, thecontour of said copy roll tending to prevent wrinkling of a compositevmoved therepast and in pressure contact therewith under the influenceof said pressure applying means.

12. A thermographic copying. machine comprising a copy roll adapted tohave a composite of a graphic original and a copy sheet moved therepastin contact with the periphery thereof, said copy roll being generallycylindrical in shape and having arr average profile in axial sectionwhich is radially inwardly bowed from its ends toward the centralportion thereof, the amountof said bow being at least 0.00015 inch perinch of length of said roll and 0.001 inch per inch of diameter of saidroll, and means for pressing a composite against the periphery of saidcopy roll as said composite moves therepast, the contour of said copyroll tending to prevent wrinkling of a composite moved therepast and inpressure contact therewith under the influence of said pressure applyingmeans.

References tilted in the file of this patent UNITED STATES PATENTS GulkoMar. 19, 1963

1. IN A THEREMOGRAPHIC COPYING MACHINE HAVING MEANS INCLUDING A ROLLDEFINING A COPY STATION, MEANS FOR IRRADIATING A COMPOSITE OF A GRAPHICORIGINAL AND A COPY SHEET WHILE IN CONTACT WITH SAID ROLL, SAID MEANSCOMPRISING A LAMP ASSEMBLY, MEANS MOUNTING SAID LAMP ASSEMBLY FORMOVEMENT BETWEEN AN OPERATIVE POSITION CLOSELY ADJACENT A SURFACE OFSAID ROLL AND A RETRACTED POSITION SPACED AWAY FROM SAIF ROLL SURFACE,DRIVE MEANS FOR SAID ROLL, AND ACTUATING MEANS OPERATIVELY ASSOCIATEDWITH SAID MOUNTING MEANS AND SAID DRIVE MEANS FOR ACTUATING SAID LAMPASSEMBLY TO OPERATIVE POSITION WHEN OPERATION OF SAID DRIVE MEANS ISINITIATED AND TO RETRACTED POSITION WHEN OPERATION OF SAID DRIVE MEANSIS TERMINATED.
 11. A THERMOGRPHIC COPYING MACHINE COMPRISING A COPY ROLLADAPTED TO HAVE A COMPOSITE OF A GRAPHIC ORIGINAL AND A COPY SHEET MOVEDTHEREPAST IN CONTACT WITH THE PERIPHERY THEREOF, SAID COPY ROLL BEINGGENERALLY CYLINDRICAL IN SHAPE AND HAVING AN AVERAGE PROFILE IN AXIALSECTION WHICH IS RADIALLY INWARDLY BOWED FROM ITS ENDS TOWARD THECENTRAL PORTION THEREOF, AND MEANS FOR PRESSING A COMPOSITE AGAINST THEPERIPHERY OF SAID COPY ROLL AS SAID COMPOSITE MOVES THEREPAST, THECOUNTOUR OF SAID COPY ROLL TENDING TO PREVENT WRINKLING OF A COMPOSITEMOVED THEREPAST AND IN PRESSURE CONTACT THEREWITH UNDER THE INFLUENCE OFSAID PRESSURE APPLYING MEANS.